Do headphones run on AC or DC?

Answer withdrawn.

DC: + and - remain constant.  Voltage fluctuation (difference between +/-) carries the sound signal which should be ideally converted directly to speaker motion.

People usually use "DC" and "AC" refer to the power supply input type accepted (and typical dynamic headphones aren't powered by an external source).  This is different than the audio signal.  The audio signal definitely changes over time, so it's AC in that sense.

Both L and R headphone inputs can be thought of as some changing values--say between -1 and +1 volts--relative to the ground at 0.  The ground can be shared because it's the reference for both channels.  So the L channel information is just the difference between what's in the L wire and the ground wire.  The L headphone driver is connected between the L wire and ground wire, so it transforms that electrical voltage difference into mechanical vibrations corresponding to that channel's signal.  Likewise, the R channel information is the difference between the R wire and the ground wire, etc.  The voltage on the L wire being negative or positive has nothing to do with whatever is on the R wire (ignoring small crosstalk), so the two signals are kept distinct despite both sharing the same ground.

edit: and the current goes from the source L output down the L wire through the L headphone driver to the ground wire and back to the source, and also from the source R output down the R wire through the R headphone driver to the ground wire and back to the source.  Maybe there's an intuitive notion that something would go down the L wire to ground and back up the R wire and thus screw up the channel separation, but it's current we're talking about.  What's of interest is the net movement of current.

I hope this explanation wasn't too rudimentary or on the flip side, unnecessarily verbose.

Btw...Yoga Fire!

Headphones and speakers run on AC. The +/- sign is there to help preserve correct phase polarity of wires so that you do not invert the signal while making the connection.  The +/- sign for headphones and speakers has very little to do with the +/- sign used for designating DC polarity.

Jack  

Speakers do NOT like DC at all,in fact if they get a good dose of it you can say goodby to them.

The polarity remains constant in a headphone, thus strictly speaking a headphone runs DC.

However, the definition of DC is often extended to the constant, zero-frequency, or slowly varying local mean value of a voltage or current, if you consider the extended definition, headphones runs neither DC or AC.

You could simply say that headphones run on the waveform of the audio signal, I think that's the most accurate answer.

Charge does reverse direction though,so AC seems to fit the bill.

Originally Posted by khaos974 

 

The polarity remains constant in a headphone, thus strictly speaking a headphone runs DC.

No, the polarity changes constantly in the rhythm of the music signal, which gets transformed into forward and backward motion of the membrane. It's clearly alternating current.
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I guess it does, I didn't think it through. Thanks.
 

Quote:

Originally Posted by JaZZ 

No, the polarity changes constantly in the rhythm of the music signal, which gets transformed into forward and backward motion of the membrane. It's clearly alternating current..

Quote:

Originally Posted by Yoga Flame 

Okay, but if headphones are AC, it has to be a different kind of AC than speakers right? The wiring is different. I mean, imagine combining the "ground" wires on conventional speakers. I'm guessing that's a big no. But stereo unbalanced headphones always have the ground wires combined at the TRS plug.

The ground on most amps is common.

If you send more than 50 mV's of DC to most headphones the coil will burn up (I've done it.)   A simple test all amp builders do when they are done is check to make sure there is no DC on the output with a DMM.   Headphones and speakers run on AC,  but some dc coupled amps have a small amount of dc current (offset),  less is always better.